腺苷三磷酸和环腺苷单磷酸对丝状真菌纤维素酶合成的调节

以虫荧光素酶法检验了四株丝状真菌在葡萄糖—无机盐液体培养过程中的胞内ATP含量。结果表明,只有当胞内ATP浓度低于10~(-S)mg/ml时,真菌才开始合成胞外纤维素酶(FPA)。以不同浓度的各种碳源培养时,菌体胞内ATP含量只要超过10~(-1)mg/ml,FPA的合成即发生阻遏。菌体胞内ATP含量与FPA合成呈显著负相关。以高效液相色谱(HPLC)法检测了菌体培养液中的cAMP含量。在非阻遏条件下,外源cAMP可以提高FPA的合成水平。但外源cAMP不能解除已经发生的酶合成阻遏。菌体ATP和cAMP水平是调节真菌纤维素酶合成的重要因子。     

L-山梨糖提高木霉纤维素酶合成速率机制的研究

在0.5％葡萄糖-Mandels盐培养液中添加终浓度为0.5％的L-山梨糖,可使里斯木霉(Trichoderma reesei C 30)和拟康氏木霉(Trichoderma pseudokoningii S38)的内切和外切β-1,4葡聚糖酶合成速率在培养的2天内提高4倍。与此同时β-葡萄糖苷酶的合成没有明显变化。L-山梨糖能明显抑制菌丝生长,但对葡萄糖的吸收没有影响,对菌丝分泌纤维素酶的机制影响不大。其对酶合成的促进可能主要是通过降低了菌丝体的生长速率。     

普通小麦×东方旱麦草属间杂种的产生及无性系的建立

本研究以普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．;２ｎ＝６ｘ＝４２,ＡＡＢＢＤＤ）为母本,以东方旱麦草（Ｅｒｅｍｏｐｙｒｕｍｏｒｉｅｎｔａｌｅ（Ｌ．）Ｊａｕｂ．ｅｔＳｐａｃｈ;２ｎ＝４ｘ＝２８）为父本,首次成功地获得了属间远缘杂种Ｆ１,其平均结实率为０．０８％。利用植物细胞工程技术,对杂种幼胚愈伤组织的诱导、胚性无性系的建立、植株再生、壮苗培养等,最终获得了生长正常的杂种Ｆ１植株。同时,通过对杂种幼胚愈伤组织、根尖细胞的细胞学观察,结果表明该杂种为真杂种,即２ｎ＝５ｘ＝３５（预期染色体数）的杂种细胞占主体;另外,因组培过程中发生了染色体数目的变异,故也有少量２ｎ＝２８－３４染色体数的细胞。以上杂种的获得为将旱麦草优异基因向小麦的转移奠定了基础。     

新型生物——人工复合血管研制的初步报告

本文设计一种由胶原和高分子聚合物组成的新型生物一人工复合血管。其研制过程是将包绕有聚酯网的硅胶棒埋入羊的皮下组织,再将形成的经聚酯网为支架的胶原管经醛化处理。作者通过肉眼和SEM观察提出了研制生物——人工复合血管的要点:聚酯网网孔要合适,其与硅胶棒的间隙要恰当,理化处理方法更要选择好。     

细胞色素c在氨基酸及二肽修饰金电极上的电化学反应

系统地研究了细胞色素ｃ在多种氨基酸和多肽修饰电极上的电化学反应。并对影响加速细胞色素ｃ电化学反应的因素进行了讨论。     

无花果蛋白酶在阴离子交换树脂上的固定化

无花果蛋白酶通过８％戊二醛活化载体,共价结合到聚苯乙烯阴离子交换树脂ＧＭ２０１上,固定化作用在ｐＨ７．７,酶浓度０．８ｍｇ／ｇ树脂,４℃下进行６ｈ。得到的固定化酶表观Ｋ_ｍ值（酪蛋白,１．１１×１０~（－４）ｍｏｌ／Ｌ）小于溶液酶Ｋ_ｍ值（１．９６×１０~（－４）ｍｏｌ／Ｌ）;固定化酶活性在ｐＨ６～８保持稳定,溶液酶最适ｐＨ为７．２;固定化酶最适温度由溶液酶的５０～６０℃移至３７℃;固定化酶２５℃保持７ｄ,重复水解酪蛋白７次后,保留８３．３％活性。固定化酶对酪蛋白水解度达４７．５％,对大豆球蛋白达１１．６％。     

昆虫杆状病毒晚期启动子在大肠杆菌中启动CAT基因表达

将油桐尺蠖（Ｂｕｚｕｒａｓｕｐｐｒｅｓｓａｒｉａ）核多角体病毒晚期基因──多角体蛋白基因启动子及５′端编码区,以两种不同方式置于缺乏启动子的氯霉素乙酰基转移酶（ＣＡＴ）基因上游,使其分别终止在不同翻译终止位点,其宿主菌具有明显不同的氯霉素抗性,最高达２００ｍｇ／Ｌ　ＬＢ培养基以上,表明昆虫病毒启动子能启动原核基因表达。对多角体蛋白基因启动子能在大肠杆菌中有效工作的原因进行了讨论。     

Anaerobic Degradation of Propionate by a Mesophilic Acetogenic Bacterium in Coculture and Triculture with Different Methanogens

A mesophilic acetogenic bacterium (MPOB) oxidized propionate to acetate and CO₂ in cocultures with the formate- and hydrogen-utilizing methanogens Methanospirillum hungatei and Methanobacterium formicicum. Propionate oxidation did not occur in cocultures with two Methanobrevibacter strains, which grew only with hydrogen. Tricultures consisting of MPOB, one of the Methanobrevibacter strains, and organisms which are able to convert formate into H₂ plus CO₂ (Desulfovibrio strain G11 or the homoacetogenic bacterium EE121) also degraded propionate. The MPOB, in the absence of methanogens, was able to couple propionate conversion to fumarate reduction. This propionate conversion was inhibited by hydrogen and by formate. Formate and hydrogen blocked the energetically unfavorable succinate oxidation to fumarate involved in propionate catabolism. Low formate and hydrogen concentrations are required for the syntrophic degradation of propionate by MPOB. In triculture with Methanospirillum hungatei and the aceticlastic Methanothrix soehngenii, propionate was degraded faster than in biculture with Methanospirillum hungatei, indicating that low acetate concentrations are favorable for propionate oxidation as well.     

Capsid assembly and involved function analysis of twelve core protein mutants of duck hepatitis B virus.

The roles of different regions of the duck hepatitis B virus (DHBV) core protein on viral capsid assembly and related functions were examined. Twelve deletion and insertion mutations which covered 80% of the DHBV C open reading frame were constructed and expressed in Escherichia coli. The N-terminal region (amino acids 3 to 66) of DHBV core protein was important for its tertiary structure and function in E. coli. The expressed core mutants without this region apparently inhibited E. coli growth. The results of transmission electron microscopy of E. coli thin sections, capsid agarose gel, and sucrose gradient sedimentation demonstrated that a few DHBV core mutants with insertion in the N terminus and deletion in the C terminus retained the ability to form core-like particles in E. coli. However, other mutations in most of N-terminal and central regions strongly inhibited the self-assembly ability of DHBV core protein in E. coli. In addition, the mutant with a C-terminal region deletion (amino acids 181 to 228) lost most of the nucleic acid-binding activity of the DHBV core protein.     

Effects of gamma irradiation on the plasma membrane of suspension-cultured apple cells. Rapid irreversible inhibition of H+-ATPase activity

The effects of ionizing radiation, used in post-harvest treatment of fruit and vegetables. were investigated on cultured apple cells ( Pyrus malus L. cv. Royal Red) on a short-term period. Irradiation (2 kGy) induced an increase of passive ion effluxes from cells and a decrease of cell capacity to regulate external pH. These alterations are likely due to effects on plasma membrane structure and function and were further investigated by studying the effects of irradiation on plasma membrane H⁺-ATPase activity. Plasma membrane-enriched vesicles were prepared and the H⁺-ATPase activity was characterized. Irradiation of the vesicles induced a dose dependent inhibition of H⁺-ATPase activity. The loss of enzyme activity was immediate, even at low doses (0.5 kGy), and was not reversed by the addition of 2m M dithiothreitol. This inhibition may be the result of an irreversible oxidation of enzyme sulfhydryl moieties and/or the result of changes induced within the lipid bilayer affecting the membrane-enzyme interactions. Further analysis of the H⁺-ATPase activity was carried out on vesicles obtained from irradiated cells confirming the previous results. In vivo recovery of activity was not observed within 5 h following the treatment, thus explaining the decrease of cell capacity to regulate external pH.
This rapid irreversible inhibition of the plasma membrane H⁺-ATPase must be considered as one of the most important primary biochemical events occurring in irradiated plant material.